Composite materials, fiber tensile members locked into place with epoxy resisns. That's the gist of it. Fibers are strong in tension and have no strength in compression (push a wet noodle why don't you!). By saturating the fibers in a resin they are locked into place next to their neighboring fibers and their buckling is generally restricted. Laying fibers at different angles from one another allows the fibers to support the tensile loads in the those varying directions. So, if you know what force vectors (direction of them) to expect it is possible to optimize the load capacity of a composite structure by only putting fibers where they are needed. This is where composites get a big win over traditional, isotropic materials, you can put the mass only where you need it and you get more effective strength for that mass because it is oriented exactly as you need.
Getting deeper into this you can also optimize the stiffness of your design by thickening its cross section - increasing its second moment area of inertia. Maximum effective stiffness comes from the outer surfaces of a cross section. Skipping the math the intuitive way to understand this is: it's easier to bend a bar if you put your hands further apart when you try to bend it. This is because your hands are further from the central axis that you are bending around - you are able to apply more torque. Similarly, when you separate the structural material in your design it is able to apply (or really, withstand) more torque - you effectively make your structure stronger, just as you feel stronger when you bend the bar.
So composites are valuable, because you can separate them with very lightweight materials, put the fibers exactly where you need them and only use mass as necessary, getting a big win mass-wise.
So this week we learned the general workflow for making a composite material. As it turned out were used burlap and epoxy. A natural fiber composite. Jean-Francoise Duval and I worked in parallel so that we could vacuum bag our parts at the same time. So the processs goes as follows: